Blackberries produce large, dark fruit clusters prized for their tart flavor and a favorite for jams and desserts. Because blackberry vines return year after year, planting blackberries assures you an annual supply of the delectable fruit. If insect pests prove a problem, however, control is essential to having a good harvest.
Many types of insects affect blackberry vines. The University of Florida IFAS Extension reports that aphids, thrips, flea beetles, scale, weevils, mites, leaf hoppers, leaf rollers, leaf miners and borers pose a possible risk to blackberry plants.
In many areas, blackberry pests are not prolific enough to recommend a spray program. Both the University of Florida IFAS Extension and the Missouri State University Extension indicate that control of insects on blackberry vines is necessary only if insect pests appear. However, the University of Florida IFAS Extension adds that, as blackberry growing becomes more popular, insect problems may occur more frequently.
Careful and frequent inspection of blackberry plants is a key to identifying insect problems. Plants affected by insects wilt, grow poorly, develop deformed leaves, and exhibit dieback of canes. Some pests, such as the raspberry cane borer and the strawberry weevil, will girdle canes just below the buds, causing the buds to drop from the plant and impacting fruit production.
According to the Missouri State University Extension, non-chemical cultural controls are most effective for several blackberry insect pests because the insects enter the plant itself and do not come in contact with the pesticide. Correctly preparing the site and providing for your plants' needs goes a long way toward promoting insect resistance. Pruning and destroying canes affected by insects helps to prevent the problem from recurring again the next year.
In some cases, chemical control of an insect infestation becomes necessary. Correct insecticide use requires accurate identification of the pest and safe, effective application of an approved insecticide. A local extension office or nursery can advise you about what insecticides are approved for use on blackberries in your area. Depending on the insect, pesticide application is most effective before, during or after blooming. The University of Florida IFAS Extension cautions gardeners to mind harvest dates and adjust insecticide applications according to safety regulations.